Communication systems often provide conference call facilities, allowing a telephone call to be shared by three or more users. In one known system, a first user, or host, calls a conference call facility to request a conference, specifying a date and time for the conference call. A telephone number is then allocated to the conference and communicated to the host for distribution to the other participants. At the appointed time, the participants dial the telephone number to join the conference. The participants may also be given a password, so that access to the conference is restricted to users selected by the host.
EP-A-1164774 discloses a system in which a conference call can be initiated by the sending of a suitable SMS to a server at a preset telephone number, with invitees being notified by SMSs sent from the server. The conference call can be joined by the invitees dialing a telephone number included in the body of the SMS invitations. However, it has been found that it is not necessarily a simple matter for an invitee to dial into the conference call. Also, it is relatively easy for invitees not to receive invitation SMSs immediately, which can prevent them joining the conference call or joining it at an appropriate time.